1. Field of the Invention
The present invention relates to an optical element for deflecting light beams, which enter and re-emerge from the latter, in such a way that their angle of emergence is limited, for use as a luminaire-cover for example, and a reflective element as a component of the optical element, as well as to corresponding methods for the production of the optical element and the reflective element.
As a result of using optical elements of the kind mentioned by way of introduction, the angle of emergence of light beams, from a luminaire for example, is limited in order to diminish any dazzlement for the viewer. In addition, of course, such an element also provides mechanical protection for the luminaire and in particular for the light source in the interior of the luminaire.
2. Description of the Related Art
Such an optical element is known, for example, from the Austrian Patent AT-B-403,403. The known element has on its side facing the lamp of the luminaire, pyramidal profiled portions that are arranged in rows and lines, so-called microprisms, which are formed as truncated pyramids and have an upper boundary face (light-entry face) that lies parallel to the base (light-emergence face). An optical element that is known from AT-B-403,403 is shown in FIG. 1 for the purposes of explanation. The whole element is made totally of a crystal-clear or transparent material.
A further optical element of the kind mentioned by way of introduction is disclosed, for example, in WO 97/36131. Various measures are known from this printed specification for preventing light beams from the lamp of the luminaire from penetrating into the intermediate areas or furrows between the top surfaces of the microprisms that form the light-entry faces, since such light beams would not emerge from the optical element at a desired angle of emergence. FIGS. 16-24 and the associated description of this printed specification, for example, disclose the possibilities of filling up the furrows between the microprisms with a filling compound that has reflective properties, coating the side walls of the microprisms with a reflective material, covering the microprism structure with a reflective mask or a grid, or providing combinations of these measures. Since the dimensions of the microprisms only lie in the range of a few hundred xcexcm, a high level of precision is required when producing such optical elements or luminaire-covers.
Basing considerations on the afore-mentioned prior art it is an object of the present invention to provide an optical element of the kind mentioned by way of introduction that has a reflective layer and which is simple to construct and therefore also to produce and at the same time has a stable structure and a high luminous quality level.
A further object of the present invention is to provide a reflective element for such an optical element that is simple to construct and therefore also to produce and at the same time guarantees a stable structure and a high luminous quality level of the whole optical element.
The optical element consists of a plate-like core of transparent material which on one side is occupied by microprisms that taper forming furrowsxe2x80x94starting from their rootxe2x80x94with, for example, all of the top surfaces of the microprisms forming the light-entry face and the other side of the core forming the light-emergence face, and with the furrows being covered by a layer that is reflective at least on one side. In accordance with the invention, furthermore, a foil of transparent material is provided that is arranged on the side of the reflective layer that is remote from the element core. The foil gives the reflective layer independent stability, something which, on the one hand, facilitates the handling thereof when the whole optical element is produced and, on the other hand, also increases the stability of the element as a whole. Furthermore, the assembly of such a reflective element on the element core of the optical element with the necessarily high level of precision is simpler to effect than the direct application of, for example, a thin metal foil to the intermediate areas of the microprism structure, as necessary in the case of the systems known previously.
The reflective layer is preferably fixedly connected to the transparent foil, in particular is welded together therewith or adhered thereto. In particular, welding has the advantage here that there is no further material component present in the system that has a refractive index which would need to be taken into consideration with regard to the luminous properties of the optical element. It is, however, also possible in the first instance to apply to, preferably vapour-deposit onto, the transparent foil a metal layer in which the desired structure is subsequently formed, something which can be effected both mechanically and by means of laser beams or else chemically.
Furthermore, a reflective layer is also preferably fixedly connected to the element core, in particular adhered thereto or welded together therewith. The connection of the reflective layer can then be effected both subsequently to prefabrication of the reflective element consisting of the reflective layer and the transparent foil and also in a joint method step at the same time as the connection of the reflective layer to the transparent foil.
Further advantageous configurations and further developments of the present invention constitute subject matter of further subclaims.